Effects Of Concurrent Endurance And Strength Training On .
Effects of concurrent endurance andstrength training on running economy andV0 2 kineticsGREGOIRE P. MILLET, BERNARD JAOUEN, FABIO BORRANI, and ROBIN CANDAUUPRES-EA 2991, Sport, Performance, Sante; Faculte des Sciences du Sport, Montpellier, FRANCE; and CREPS deMontpellier, Montpellier, FRANCEABSTRACTMILLET, G. P., B. JAOUEN, F. BORRANI, and R. CANDAU. Effects of concurrent endurance and strength training on runningeconomy and VO 2 kinetics. Med. Sci. Sports Exerc., Vol. 34, No. 8, pp. 1351-1359. 2002. Purpose: It has been suggested thatendurance training influences the running economy (CR) and the oxygen uptake (VO2 ) kinetics in heavy exercise by accelerating theprimary phase and attenuating the VO2 slow component. However, the effects of heavy weight training (HWT) in combination withendurance training remain unclear. The purpose of this study was to examine the influence of a concurrent HWT endurance trainingon CR and the VO2 kinetics in endurance athletes. Methods: Fifteen triathletes were assigned to endurance strength (ES) orendurance-only (E) training for 14 wk. The training program was similar, except ES performed two HWT sessions a week. Before andafter the training period, the subjects performed 1) an incremental field running test for determination of VO2, and the velocityassociated (V402m.), the second ventilatory threshold (VT2): 2) a 3000-m run at constant velocity, calculated to require 25% of thedifference between VO2 m,, and VT2 to determine CR and the characteristics of the VO2 kinetics; 3) maximal hopping tests to determinemaximal mechanical power and lower-limb stiffness; 4) maximal concentric lower-limb strength measurements. Results: After thetraining period, maximal strength were increased (P 0.01) in ES but remained unchanged in E. Hopping power decreased in E (P 0.05). After training, economy (P 0.05) and hopping power (P 0.001) were greater in ES than in E. VO2 m ,,,leg hopping stiffnessand the VO2 kinetics were not significantly affected by training either in ES or E. Conclusion: Additional HWT led to improvedmaximal strength and running economy with no significant effects on the VO2 kinetics pattern in heavy exercise. Key Words:ENERGY COST, MAXIMAL OXYGEN CONSUMPTION. OXYGEN UPTAKE SLOW COMPONENT, HOPPING POWERT he combined effects of concurrent strength andinfluence (29) on the economy. Paavolainen et al. (22,23)investigated the effects of explosive-strength training inwell-trained athletes, but the effects of concurrent heavyweight training (HWT) and endurance training on economyhave not been studied in elite athletes.At the highest submaximal intensities, above the lactate threshold, CR represents only the aerobic contribution to the total energy expenditure (9), and this aerobicpart tends to rise slowly. The slow component of oxygenuptake kinetics in long-term constant-rate exercise can bedescribed as an increase in the energy expenditure abovethat predicted from submaximal V0 2-work rate relationship, leading to a reduced work efficiency (10). Severalstudies (5,6,10,21,24,28) have shown that endurancetraining results in a change in V0 2 kinetics, so that ashorter constant time of the primary phase (21,24) and areduced amplitude of the V02 slow component occurs(5,10,28). It was proposed that around 85% of the V0 2slow component is located at the muscular level (10) andthat central factors have only a minor influence on itsamplitude. A limited V02 slow component has beensuggested to be an important parameter of the enduranceperformance (10). However, to the best of our knowledge, very little is known on the effects of strengthtraining on the characteristics of the V0 2 kinetics, especially the parameters that described the primary phaseand the slow component (29). Therefore, the purpose ofendurance training on the endurance performanceTof untrained (12,16,18,19,25) or trained athletes(13,14,22,23) have been extensively studied. There is evidence to suggest that endurance training inhibits maximalstrength development, mainly a few weeks after commencement of a concurrent training regime (25). It has beensuggested that although strength training does not interferewith the development of the maximal oxygen uptake(VO2max) (11-12,18), it could lead to improvement of endurance performance of untrained (11,12,18,19,25) or moderately trained athletes (13).It has been well documented that the speed achieved inendurance competition relies not only on the rate of energyexpenditure but also on the energy cost (CR) of the considered locomotion (9). It also appears that CR is a betterpredictor of endurance performance than VO2max in a homogeneous group of athletes (8). However, the effects ofconcurrent strength and endurance training on economy inwell-trained endurance athletes are still unclear. It has beenargued that strength training improves (13,14,23) or has no0195-913 1/02/3408-1351/ 3.00/0MEDICINE & SCIENCE IN SPORTS & EXERCISE,Copyright 2002 by the American College of Sports MedicineSubmitted for publication September 2001.Accepted for publication March 2002.1351
TABLE 1. Main characteristics of the endurance strength (ES)and endurance-only (E)triathletes.Training CharacteristicsES(N 7)E (N 8)Age(yr)Height(cm)Weight(kg)TotalTraining(yr)24.3 5.221.4 2.1175.4 9.1175.4 5.467.4 8.865.0 7.47.0 2.66.6 1.7Swimming1(knmnwk)18.3 t 5.019.8 4.0Cycling(km.wk- 1)221 49210 50Running(km.wk- 1)Stretching(h.wk-')Amount(h.wk-')48 744 51.6 0.51.6 0.520.5 3.820.3 3.0Weight, pretraining weight.the present study was to examine the effects of a regimeof maximal strength training, in combination with anexisting endurance-training program, on the runningeconomy in well-trained triathletes. Furthermore, thisstudy was conducted to determine whether strength training influences the V0 2 kinetics during heavy constantrate running exercise.METHODSApproach to the problem and experimental design. The hypothesis that combined HWT and endurancetraining would lead to greater lower limb strength, power,and stiffness and be more transferable to a better runningeconomy than endurance-only training was tested. To answer this question and compare the impacts of a combinedversus an endurance-only training, we chose two differenttraining regimes, suitable for inclusion in the winter schedule of national and international-level triathletes, over a longperiod of 14 wk, a duration classically observed in theendurance sports. A field-based approach was applied toevaluate both realistic central and peripheral adaptationsthat could influence the performance.Subjects. Fifteen well-trained subjects were randomlyassigned to the endurance-strength training group (ES; N 7) or to the endurance-only group (E; N 8). Seven ofthem, practicing at an international level (elite nationalteam), were matched in the two groups (three in ES and fourin E). All the subjects agreed to participate in the study ona voluntary basis. The study was approved by the institutional ethics committee, and all subjects provided written,voluntary, informed consent before participation. The subjects were all fully familiar with testing procedures, havingregularly being tested as part of their training evaluation.The physical characteristics of the two groups are shown inTable 1.Methods. Before and after a controlled training period,all subjects performed field and laboratory-based runningand muscle function tests. The first test involved an incremental running test to exhaustion to determine the maximaloxygen uptake (VO2 max), the velocity associated withVO2max (VV02max)7 the velocity associated to the secondventilatory threshold (VvT2), and the velocity associated tothe intensity termed A25% (VA25%), corresponding toV02 vT2 plus 25% of the difference between V0 2 vT) andV02max. The second test comprised a 3000-m run at acontrolled constant VA25% preceded by 6 min at 75%VV02max to determine running energy cost at the two intensities (CR 75 % and CRA2 5%) and record breath-by-breath1352Official Journal of the American College of Sports MedicineV0 2 data to model V0 2 kinetics during exercise. A thirdseries of tests included maximal hopping tests at a 2-Hzfrequency to determine the maximal mechanical hoppingpower and lower-limb hopping stiffness. A forth series wasmaximal concentric lower-limb strength measurements.General training. The training period lasted for 14 wkand was carried out during the winter period, when thesubjects were not involved in any competitions. The trainingperiod started after a 10-wk preconditioning-orientationphase, where the subjects restarted consistent training. Allathletes were experienced and members of a residentialtraining center where they were under the control of professional trainers. Moreover, they recorded training exercises in a diary that was reviewed regularly. The vast majority of the training during this basic period was strictlyaerobic, realized under 70% of VO2 (Table 1). Stretchingremained constant (1.6 0.5 h-wk-1) in the two groups.Strength training. In addition to the endurance training, the ES group performed an HWT session of lower-limbmuscles twice a week. Exercises (i.e., hamstring curl, legpress, seated press, parallel squat, leg extension, and heelraise) were exclusively focused on quadriceps, hamstring,and calf muscles. Workouts consisted of two warm-up setsfollowed by three to five sets to failure of 3-5 reps. Thetraining program was periodized and was composed ofseveral 3-wk periods. In each of these periods, the numberof sets increased (i.e., three in the first week, four in thesecond week, and five in the third week). The loads werecalculated 90% one-repetition-maximal (lRM) and wereprogressively increased to maintain this range of repetitionsper set. Reassessment of IRM was completed by the ESgroup every 3 wk to maintain maximal loads over the wholetraining period.Testing. The ES and E groups were examined beforetraining and after the training period. The testing protocolwas conducted over two consecutive days on a 400-m synthetic track, then an additional day in the following week inthe laboratory for concentric strength and hopping tests. ESperformed supplementary maximal strength tests at week 6.Maximal concentric lower-limb strength measurements. Maximal concentric strength evaluation wasperformed using two exercises (half-squat and heel raise) byall athletes before and after the training period. After awarm-up workout, the subject's near-maximal load wasapproximated by the trainer to be around 90% of the previous best load of the subject. The load was graduallyincreased until the subject could lift the resistance once butnot twice. This load was therefore defined as 1RM. For thehalf-squat, the starting position was at a knee angle of 1200,http://www.acsm-msse.org
and the exercise was performed in a guided strength rack,ensuring maximal security. The amplitude of the movementwas controlled by the trainer. For the heel-raise exercise, thestarting position was a standing position with straight legs.Because the resistance was maximal, two assistants helpedthe subjects to position the bar correctly over the shoulders,to prevent any accident.Hopping tests. Maximal vertical rebounds on both legswere executed by the subjects from a standing position at 2Hz for 10 s before and after the training period. Subjectswere instructed to rebound to the highest possible point withthe smallest ground contact times and to keep hands on thehips throughout the hops (4,7). Flight time (tf) and groundcontact times (tj were recorded by an apparatus consistingof a digital timer connected to a contact mat (Powertimer,Newtest, Oulu, Finland) with an accuracy of 1/100 s. Asdescribed previously (4,7), the displacement of the center ofmass during the flight (hf) and the maximal mechanicalpower of the positive work (P) of the subjects werecalculated:hf (g-t, 2)/8 (hop height, in m)(1)P (mtg2 rtJ1,)/(4.tc) (maximal hopping power, in W)(2)where m the body mass of the subject, t4 is the total time-ofthe hop (t, tc tf), and g is the gravitational acceleration.The vertical stiffness of the lower limbs (Kven, N.m.kg 1)is the force change/length change ratio and was calculated,as described previously (7):The initial velocity was set as 8 knm-h1 under the estimated VV02max. The duration of the test was expected to bebetween 15 and 20 min. The increments of velocity were setat 0.5 km h-1 for stages of 1 min. The subject adjusted hisvelocity to sound signals and visual marks at each 20-minterval around the track. All subjects were familiarizedwith this procedure, having completed similar paced exercise sessions during training. All subjects were encouragedto perform their best effort. Breath-by-breath data wereaveraged over 30 s, and V0 2m,ax was defined as the highest30-s value reached. VV0O2ma was determined as the minimalvelocity at which VO2mrax was reached. The second ventilatory threshold (VT 2) was defined by 1) a systematic increase in VE/NO2 , 2) a concomitant nonlinear increase inthe VE/VCO 2 , and 3) a decrease in the APET 02 (differencein the inspired and end-tidal 02 pressure). VT2 was determined by two independent observers.3000-m test at V,225 %. On the second day, the subjectsperformed a 3000-m run at VA25%.The subjects warmed up6 min at -60%VVo 2mna followed by 6 min at a controlledis the intenV7 5 % velocity, where V75 % 0.75 X VV02mansity where a V0 2 slow component has been previouslyobserved (6). Before the start of the 3000 m, the subjectsrested for 5 min to determine VO 2b. CR7 5% and CRA25% (inmL 0 2 .kg- 1 .km ') were calculated from the averaged 3rdto 4th-min V0 2 above basal metabolic rate (BMR), at respectively the V75% warm-up and the VA2 5% 3000 m, asfollows:CR (VO2 - 0.083) X V-lKve, m.nr2 (lower limbs hopping stiffness, in kNlmrn'kg-')(3)with tan(7r-(w tJ2)) - tf(4).rwhere &Ois the forced oscillation of the body while verticalhopping. With tf and tc as known variables, equation 4 canbe solved and coO determined.Track running tests. The following respiratory gasexchange variables were collected, using a breath-by-breathportable gas analyzer (Cosmed K4b2 , Rome, Italy):VO 2,VCO2 pulmonary ventilation (VE), ventilatory equivalents for oxygen (VE/V0 2 ) and carbon dioxide (VE/VCO2 ), end-tidal P0 2 (PET 02 ), and PCO2 (PETc02 ). Calibration procedures were performed before each testaccording to the manufacturer's instructions. Heart rate(HR) was recorded by the K4b2 via a portable HR monitorbelt (Polar Electro, Kempele, Finland). At the end of thetests, subjects indicated their rating of perceived exertion(RPE) using a 6-20 scale. All tests were preceded by a5-min standing rest to determine the V0 2 baseline (VO 2b).Incremental test to exhaustion. The subjects performed first the incremental test to exhaustion on a 400-mrunning track to determine the maximal oxygen uptake(VO 2m,ax), the velocity associated with V0 2 (VV0 2 max), andthe velocity associated with the second ventilatory threshold(VVT 2). In addition, the velocity (VA259) corresponding toV0 2 vm plus 25% of the difference between V0 2 vy2 andVO2.ax, was calculated.A25% VO2 vT 0.25 X (VO 2 mSTRENGTH AND ENDURANCE TRAINING-V'O 2 VT2-(5)(6)twhere V0 2 is expressed in mL-kg- .s-1, 0.083 mL.kg-'ls'1is the y-intercept of the V0 2-velocity relationship of youngadults, and V is expressed in m-s- 1. At posttraining, VA25 was reactualized per sine.Kinematic variables and running leg stiffness.Average stride frequency (SF, in Hz) and stride length (SL,in m) were recorded eight times, over a 100 m of each lap(SF X SL average velocity over 100 m). The averagevalues over the 3000-m were retained. The average posttraining running leg stiffness was approximated with theequation 3 from tf and t,, with t, measured at each lap withthe contact mat (Powertimer).V0 2 kinetics. To describe the V0 2 kinetics, a classicalexponential model was used (1,3).V0 2 (t) VO2b Al{l - e[(t-td 'llU,Phase 2 (primary component) A2 [1 -Phase 3 (slow component)(7)whereU1 Ofort td, and Ul I fort - td,U2 0 for t td2 and U2 I for t td2(8)VO2b is the V0 2 at rest, Al and A2 are the asymptoticamplitude, td, and td2 are the time delays after the start ofthe exercise, T, and T2 are the constant times, respectively,for the second and third phase. Because the primary phaseis not distorted by any cardiodynamic influence, the firstMedicine &Sciencein Sports &Exerciseb1353
90 -Aso -TABLE 2. Measured parameters during the track running incremental test toexhaustion, before and after training in the endurance-strength (ES) and enduranceonly (E)triathletes.70 -60EIncremental Test to ExhaustionvozmaxVT2HR(mL.min-'.kg- 1)(%V02m.,)(bpm)-50 -1 40-30-20-* V02 measured-V02 modeled10 -;010020030040050060010 -'.0-.E jJ. .:.:.-:-5 --10 -15 -0100200300400500600Time (s)RESULTSFIGURE 1-Example for subject 1: fit of the modeled 02 uptake in theheavy constant-rate exercise (A) and distribution of the residual sum ofsquares (B).20 s were not taken account in the calculation of the parameters of the primary phase (TI and Al). The amplitude ofthe V0 2 slow component was defined as A' 2A'2 A2 {1 - e- t( - Ld )h l(9)where te is the time at the end of the exercise.As described previously (3), the parameters of the modelwere calculated by an iterative procedure by minimizing thesum of the mean squares of the differences between themodeled VO 2 and the measured VO2 (see subject 1 in Fig.IA). The values of the measured breath-by-breath VO2 thatwere outside a three standard deviations range from themodeled V0 2 were removed, representing less than 0.5% ofthe data collected. The time delay for the slow componentphase (td2) was fixed to be higher than the time of the firstexponential component for reaching A',, where A', 2 99%A1. A Fisher test was used to determine the degree ofsignificance of the exponential model. The distribution ofresidual errors between the modeled and the measured V0 2as a function of time was tested using linear and nonlinearregressions.-Statistical analysis. Paired t4ests were used to determine the significance of differences in the measured variables before versus after training. When the normality testfailed, a Mann-Whitney rank sum test was performed between pre- and post-training variables. A repeated measures1354ES(N 7)Pretraining69.7 3.688.4 2.8189 1016.0 1.4Posttraining67.2 4.488.1 t 5.0189 1116.3 0.5E (N 8)Pretraining67.6 6.489.3 8.1190 516.5 1.7Posttraining67.3 5.688.8 6.4189 516.5 1.4Values are means SD. VO2max,maximal oxygen uptake; VT2, second ventilatorythreshold; HR, maximal heart rate; RPE, rating of perceived exertion.ANOVA was used to identify differences between the twogroups of subjects, by examination of the group X timeinteraction. Statistical power was determined to be from0.57 to 0.69 for the sample sizes used at the 0.05 alpha level(SigmaStat, Jandel Corporation, San Rafael, CA). Effectsize (ES) was calculated for each test and displayed forevery significant effect. Pearson correlation coefficientswere used to examine the relationships between change ofeconomy and change of power, stiffness, or strength variables. The results are presented as means SD. For allstatistical analyses, a P-value of 0.05 was accepted as thelevel of statistical significance.15-ARPE(points)Official Joumal of the American College of Sports MedicineThe main characteristics of the endurance training of thetriathletes -are presented in Table 1. No differences wereobserved in the training parameters between ES and Eduring the period studied.Table 2 shows the effect of the 14 wk of training on thephysiological variables during the incremental track-running test. VV0 2 max VT2 did not differ significantly betweenthe groups before training. During the training period, therewas a significant increase (P 0.01) in the velocity associated with VO 2max for ES (from 19.5 1.0 to 20.0 0.8km.h-1 ; ES 0.57) but not for E (from 19.3 1.0 to 19.8 1.2 km.hI'; ES 0.39) (Fig. 2A). V0 2 max, VT 2(%VO2max), maximal heart rate, and the rating or perceivedexertion remained unchanged with training in the twogroups.Table 3 shows the effects of training on the physiologicalvariables and on the parameters of the modeled V0 2 kineticsduring the 3000-m run at A25% intensity. Significant groupby-training interactions were found in running economyafter 14 wk of training, both below VT2 at 75%VV02 max (F 5.0; P 0.05; ES 1.16) or above VT 2 at A25%92%VV0 2 max (F 8.0; P 0.05; ES 1.46). Beforetraining, both CR7 5% (193.6 4.3 vs 189.8 t 13.1nL.kg-1 .km- 1) and CRA25% (196.4 5.5 vs 194.6 22.3mL.kg- 1 km-') did not differ significantly between ES andE. After training, CR7 .5% (180.2 20.0 vs 203.2 20.2mL-kg-1 -km7l; ES 1.14) and CRA25% (185.4 16.3 vs205.2 18.1 mL.kg-l.km- 1; ES 1.15) wer6 significantly(P 0.05) lower in ES than in E (Fig. 2B). No significantdifferences or -changes during the training period were obhttp://www.acsm-msse.org4
22-0.12. The sum of residual errors ( 10-4) was distributedrandomly around zero (Fig. IB) and similar in the twogroups. No significant regression was found between theresiduals and the time, indicating that the model was appropriate to describe the 02 uptake kinetics and that no furtherimprovement in the model could have been proposed. Before training, ES had faster V0 2 kinetics with smaller constant times for the second and third phases than E. However,it is of interest to note that the constant times for phase 2were unchanged during the training period in either the ESor E group. In addition, the amplitude of the slow component remained unchanged in the two groups during thetraining period.As required, the velocity was kept constant along the3000-m test with a coefficient of variation (CV) of 1.6 0.6% between the different laps. No significant differencesor changes after the training period were observed in eitherthe ES or E groups in stride frequency (1.52 0.07 and 1.47 0.08 Hz at pretraining, and 1.53 0.08 and 1.52 0.05Hz at posttraining, respectively, for ES and E) or stridelength (3.19 0.24 and 3.28 0.18 m at pretraining, and3.22 0.28 and 3.23 0.24 m at posttraining, respectively,A20isE141210250BEi200E2:,E0o 1000)4 500C4500 4000 -for ES and E) during the VA25 % 3000 m. The method used2500-0.cm 2000-ac15000z1000500EESwitithVtwoa.FIGURe 2-Change im (A) the velocity associated(Vvo 2 , knwha'); (B) the runnimg economy (mLekgo -kmn); and (C)the maximal hopping power (W), between pre- (wstite bar) and posttraining (black bar) in the endurance-strength (ES; N 7) and endur2ance-only (E; N 8) groups. *P 0.05, **P 0.01.served in either the ES or E groups in Vo 25 % end-exerciseHR or RPE during the VA25 % 3000 m.The kinetics of the VOu response were modeled with twoexponential terms (1) in all subjects, as the exercise durationwas always longer than the constant time of the slow component. In other words, in the present study, the use of alinear term instead of an exponential function would haveresulted in a lower fit. The coefficient of determnination (R 2)between the measured and the modeled V02 was 0.73 to approximate the running leg stiffness led to a slightlygreater variability in contact time (159 7 vs 169 9 ms,ES 1.2; and between-measures CV 5.4% vs 4.2%,respectively, for ES and E) and thus in stiffness (betweenmeasures CV 7.3 1.9% vs 6.0 1.9%, respectively, forES and E). After training, ES had a significantly greater (P 0.05) run leg stiffness (643 59 vs 575 58N-m- 1.kg-'; ES 1.2) than E.Table 4 shows the effect of training on the body weight,maximal strength, and variables measured during the hopping tests. Before training, maximal strength, contact time,hopping power, and hopping stiffness did not differ significantly between ES and E. Significant group-by-traininginteractions were found in the maximal strength (P 0.01)between ES and E during the training period; ES increasedsignificantly the maximal strength (P 0.05) as expressedby IRM both on the half-squat and on the calf raise exercises, whereas the values of strength did not change in theE group. Significant group-by-training interactions werefound in hop height (F 8.83; P 0.05; ES 0.60) andhopping power (F 5.14; P 0.05; ES 0.55) during thetraining period. ES maintained hop height unchanged,TABLE 3. Measured and calculated parameters during the constant-velocity 3000-m test, before and after training in the endurance-strength (ES)and endurance-only(E)triathletes.3000-m at Constant VelocityA2T2td2A,xtd,BLRPEHRV4,25%1(s)(s)(mL min-'.kg' )(s)(s)(mL.min- 1'kg-')(points)(mL-min- 1'kg- 1)(km.h- 1)(bpm)ES(N 7)PretrainingPosttrainingE (N 8)PretrainingPosttraining17.4 0.917.6 0.8181 11185 1114.7 1.114.9 0.911.2 5.812.0 5.58 7- 6 713 6*15 646.4 9.444.2 9.965 3983 4361 32*84 766.7 4.35.1 3.73.7 3.3191 14286 8346.1 8.58 7 21 611.5 4.114.8 1.417.2 1.1 186 54.6 3.7165 16047.9 8.7102 837 7 17 915.1 t 1.012.5 4.617.5 1.1 187 5Values are means SD. VA25 Y,velocity associated with A25% VT2 0.25 x (VO2ma* - VT2): HR. end-exercise heart rate: RPE, rating of perceived exertion; BL, baseline: td,and td2, time delays; Tr and T2,time constants: A1 and A2, amplitude of, respectively, the fast primary component and the slow component of the V02 response.*P 0.05 for differences between groups.STRENGTH AND ENDURANCE TFWNINGMedicine &Science in Sports &Exerciseo1355
TABLE 4. Body weight, maximal strength, and measured and calculated parameters during the hopping tests before, at mid-, and after training in the endurance-strength (ES)and endurance-only (E)triathietes.Weight(kg)Maximal Strength.1 RM Half-Squat1 RM Heel Raise(kg)(kg)ES(N 7)Pretraining67.4 8.8214 27224Midtraining (week 6)67.5 8.7Posttraining (week 14)67.1 8.7268 16*##E261E (N 8)Pretraining65.0 7.4200 28197Posttraining (week 14)64.0 6.8208 27198Values are means SD. 1 RM, maximal weight on one repetition.* P 0.001 for differences between groups; # P 0.05; ##P 0.01 for differencesand post-training.whereas E had a significant decrease (Table 4). Hoppingpower was significantly lower after than before the trainingperiod in E (2625 631 W and 2963 535 W, respectively; P 0.05; ES 0.58) but.not in ES (3232 412 Wand 3410 720 W, respectively) (Fig. 2C). Although hopping stiffness (in kN*m-1) and hopping power (in W) weresignificantly correlated at pre- (r 0.58; P 0.05) andpost-training (r 0.66; P 0.01),,no significant changes ordifferences were found in either the ES or E group in contacttime or hopping stiffness, expressed in kNmr-1 orN-m-1.kg-1. A significant (r -0.55; P 0.05) correlation was observed between the change of CRA2 5% and thechange of hopping power during the training period.DISCUSSIONThe present study shows that additional heavy-strengthtraining yields a positive influence on the running economyof well-trained triathletes. During the training period, thechange in running economy was moderately correlated tothe change of hopping power. In addition, heavy-strengthtraining did not alter the V0 2 kinetics in heavy constant-rateexercise.Change of running economy. The results of thepresent study are in line with previous studies (13,14,23)that reported improvement of the economy after a combinedstrength endurance training in endurance athletes, whereasno change in endurance-only athletes. Paavolainen et al.(23) showed that 5-km performance, running economy. and"muscle power" of well-trained athletes improved after 9wk of explosive-strength training, whereas no changes wereobserved in a control endurance-training group. However,explosive-strength training leads to different muscular adaptations than typical HWT used in the present study. Forexample, a greater increase in the rate of activation of themotor units (17) has been described as one of the mainmechanisms for improvement of neuromuscular characteristics related to improved (23) or unchanged (22) aerobicperformance characteristics.It is well established that long-term endurance trainingand maturation improve running economy in nontrainedathletes or sedentary subjects (8)., However, because welltrained endurance athletes have a narrow margin of improvement in aerobic capacity after several years of training1356Official Journal of the American College of Sports Medicine 17Contact Time(ms)Hopping TestsHop Height(m)Stiffness(N.m- 1.kg- 1 ) 21*##E147 19144 18143 100.274 0.0350.269 0.0250.283 0.043*#581 124601 128592 51 24 25159 23158 310.273 0.0310.240 0.047E506 115524 177between groups in the effects of training; P 0.05 for differences between pre-(23), the lack of significant running economy improvementin the two groups is not surprising. The group-by-traininginteraction was observed in CR during the training periodwithout any similar interaction between groups in VO 2ma,or VT2 . In parallel, similar group-by-training interactionswere observed in maximal strength and hopping power.These results underline a specific effect of the heavy weighttraining and support the view that limiting factors of endurance performance in well-trained athletes may be morestrongly related to local/peripheral than to central factors(10,20,23). The importance of the so-called "muscle power"defined as the neuromuscular system's ability to producepower at the highest exercise intensity, when the musclecontractility may be limited, is therefore emphasized (23).Several factors can be proposed to explain the improvementof running economy after strength training.For the same level of muscle tension, Type II motor unitsare recruited preferentially at lower cycle frequency, whenthe force required at each cycle is higher. If the stridefrequency remains unchanged, the improv
economy than endurance-only training was tested. To an-swer this question and compare the impacts of a combined versus an endurance-only training, we chose two different training regimes, suitable for inclusion in the winter sched-ule of national and inte
Endurance training. Endurance training was per- formed on a cycle ergometer (Monark). The training consisted of five 3-m bouts at a power output corre- sponding to 90-100% VOW max. In group A, which trained only one randomly assigned leg for endurance, 3-min rest periods intervened between successive bouts. Group B
Concurrent coding features Concurrent Coding Dashboard is the launch padfor concurrent coders: Manage workflow Complete final coding Concurrent Coding Worklists Can be defined like CDI worklists Priority factors that support concurrent coding workflow ocase status, priority score, last coder, last reviewer Ability to add findings .
lete. Elite endurance athletes exhibit remarkable aerobic power. They can sustain relatively high-velocity move-ments for hours that an untrained in-dividual may only be able to maintain for several minutes before fatiguing. Figure 12.1 muscular endurance The ability of a muscle or gro
engine Briggs & Stratton Endurance 625ex Briggs & Stratton Endurance 725exi Briggs & Stratton Endurance 725ex Briggs & Stratton Endurance 775ex engine Displacement (cc) 150 163 190 175 starting system autochoke autochoke autochoke autochoke Wheel size – front / rear (in.) 8 / 8 8 / 11 8 / 8 8 / 8 cutting Width (in.) 22 22 22 22
We adopt a model-based approach for the design and construction of concurrent programs Models finite state machines to represent concurrent behavior Practice Book uses Java for constructing concurrent programs We will be presenting numerous examples to
Sports Science Exchange (2014) Vol. 27, No. 136, 1-5 1 KEY POINTS Very few sports use only endurance or strength. Outside of running long distances on a flat surface and powerlifting, practically all sports require some combination of endurance and strength. Endurance and
aerobic-capacity training to target goals, and training protocols for speed endurance and strength endurance. Attendees will learn to assess aerobic fitness, create paced workouts and pro-gramming based on heart rate, and create dynamic warm-ups. Overall, trainers will learn how to use endurance-training meth-
par catégorie alimentaire. A partir des informations disponibles dans les listes d’ingrédients, il est parfois délicat pour un même libellé d’ingrédient de différencier son utilisation en tant qu’additif ou en tant que substance à usage d’enrichissement (exemple : acide ascorbique). Pour ce rapport et pour ces substances, il a été décidé, par convention (choisie), de .
